[ovs-discuss] 回复: OVN LSP with a unknown in address will not build arp response lflows

鲁 成 lucheng0127 at outlook.com
Fri Nov 5 03:45:57 UTC 2021


Thanks it solved my confusion.


Shawn.Lu
Software engineer of EasyStack
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发件人: Daniel Alvarez Sanchez<mailto:dalvarez at redhat.com>
发送时间: Thursday, November 4, 2021 9:43 PM
收件人: 鲁 成<mailto:lucheng0127 at outlook.com>; bugs at openvswitch.org<mailto:bugs at openvswitch.org>
主题: Re: [ovs-discuss] OVN LSP with a unknown in address will not build arp response lflows

adding the list back

On Fri, Oct 29, 2021 at 10:04 AM 鲁 成 <lucheng0127 at outlook.com<mailto:lucheng0127 at outlook.com>> wrote:
When it come to me, I think LSP with address "fa:16:3e:b3:c0:e5 192.168.111.42" and unknown
unknown it means port can send traffic with any mac address
But for address "fa:16:3e:b3:c0:e5”, maybe we should make an arp reply for this address, don’t you think?

This used to be the former behavior but we hit use cases where a VM could send traffic from a particular port with that IP address (192.168.111.42 in your example) but a different MAC.
An example of this use case is NIC teaming where an IP fails over to a different port but the MAC address is different.

The patch that changed this behavior is here:

https://patchwork.ozlabs.org/patch/1258152/

Hope it helps!
daniel


Thanks
从 Windows 版邮件<https://go.microsoft.com/fwlink/?LinkId=550986>发送

发件人: Daniel Alvarez Sanchez<mailto:dalvarez at redhat.com>
发送时间: Friday, October 29, 2021 3:58 PM
收件人: 鲁 成<mailto:lucheng0127 at outlook.com>
抄送: bugs at openvswitch.org<mailto:bugs at openvswitch.org>
主题: Re: [ovs-discuss] OVN LSP with a unknown in address will not build arp response lflows

Hi,

On Fri, Oct 29, 2021 at 5:50 AM 鲁 成 <lucheng0127 at outlook.com<mailto:lucheng0127 at outlook.com>> wrote:
Environment info:
OVN 21.06
OVS 2.12.0
Reproduction:
1. Create a port with neutronclient assign it to a node and close port security group
2. Create a ovs port and add it to br-int, and set interface iface-id same as neutron port uuid
After it Neutron will create a LSP in OVN NB, and append unknow into LSP’s address field
Check it in script[1]

Port info:
()[root at ovn-tool-0 /]# ovn-nbctl find Logical_Switch_Port name=6a8064f9-f2cc-407d-b8da-345c6a216cb3
_uuid               : 88fd1a84-8695-4cef-b916-45531edaf0db
addresses           : ["fa:16:3e:b3:c0:e5 192.168.111.42", unknown]
dhcpv4_options      : 1a8ca1af-519c-4aa2-b3a3-cc74955dee1f
dhcpv6_options      : []
dynamic_addresses   : []
enabled             : true
external_ids        : {"neutron:cidrs"="192.168.111.42/24<http://192.168.111.42/24>", "neutron:device_id"="", "neutron:device_owner"="", "neutron:network_name"=neutron-6ac00688-422f-4a4f-99ae-b092b2d87f7b, "neutron:port_name"=lc-tap-2, "neutron:project_id"="498e2a96e4cc4edeb0c525a081dd6830", "neutron:revision_number"="4", "neutron:security_group_ids"=""}
ha_chassis_group    : []
name                : "6a8064f9-f2cc-407d-b8da-345c6a216cb3"
options             : {mcast_flood_reports="true", requested-chassis=node-1.domain.tld}
parent_name         : []
port_security       : []
tag                 : []
tag_request         : []
type                : ""
up                  : false

Results:
OVN will not build arp responder lfows for this LSP


I believe that this is the expected behavior as you disable port security, meaning that the traffic from that port can come from any MAC address (it's unknown to OVN). Hence, it is up to the VM/container/whatever to reply to ARP requests and OVN should not reply on its behalf.

Hope this helps.

Thanks!
daniel



Script:
[1]:
#!/usr/bin/bash

# Create port
# neutron port-create --name lucheng-tap --binding:host_id=node-3.domain.tld share_net

HOST=""
MAC=""

get_port_info() {
    source openrc
    port_id="$1"
    HOST=$(neutron port-show -F binding:host_id -f value "$port_id")
    MAC=$(neutron port-show -F mac_address -f value "$port_id")
    ip_info=$(neutron port-show -F fixed_ips -f value "$port_id")
    echo Port "$port_id" Mac: "$MAC" HOST: "$HOST"
    echo IP Info: "$ip_info"
}

create_ns() {
    port_id="$1"
    iface_name="lc-tap-${port_id:0:8}"
    netns_name="lc-vm-${port_id:0:8}"
    ssh "$HOST" ovs-vsctl add-port br-int "$iface_name" \
      -- set Interface "$iface_name" type=internal \
      -- set Interface "$iface_name" external_ids:iface-id="$port_id" \
      -- set Interface "$iface_name" external_ids:attached-mac="$MAC" \
      -- set Interface "$iface_name" external_ids:iface-status=active

    ssh "$HOST" ip netns add "$netns_name"
    ssh "$HOST" ip l set dev "$iface_name" address "$MAC"
    ssh "$HOST" ip l set "$iface_name" netns "$netns_name"
    ssh "$HOST" ip netns exec "$netns_name" ip l set lo up
    ssh "$HOST" ip netns exec "$netns_name" ip l set "$iface_name" up
}

main() {
    get_port_info "$1"
    create_ns "$1"
}

main $@
neutron port-update --no-security-groups [port uuid]
neutron port-update --port_security_enabled=false [port uuid]

What I found:
When try to build_lswitch_arp_nd_responder_known_ips in ovn northd, it will skip LSP, which has unknow flag.
static void
build_lswitch_arp_nd_responder_known_ips(struct ovn_port *op,
                                         struct hmap *lflows,
                                         struct hmap *ports,
                                         struct ds *actions,
                                         struct ds *match)
{
    ...
            if (lsp_is_external(op->nbsp) || op->has_unknown) {
                return;
            }

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